Non rifling drill bit

ABSTRACT

THE BIT IS FOR HARD ROCK ROTATIVE PERCUSSIVE DRILLING AND INSTEAD OF THE BODY OF THE BIT DECREASING IN DIAMETER FROM THE TIPS OF THE INSERTS, ADDITIONAL BODY METAL IS PROVIDED IN ONE FORM OR ANOTHER AROUND THE HEAD SPACED BELOW THE INSERTS, TH STEADY THE BIT IN THE HOLE AND HAVING AN OUTER DIAMETER EQUAL TO OR JUST LESS THAN THE TRUE DIAMETER OF THE HOLE. THIS KEEPS THE BIT TRUE DURING THE PERCUSSIVE ROTATION ACTION AND ELIMINATES OR SUBSTANTIALLY REDUCES RIFLING.

p 20, 1971 I. BERSCHEID 3,605,925

NON RIFLING DRILL BIT Filed Sept. 2, 1969 2 Sheets-Sheet 1 p 20, 1971 I. BERSCHEID 3,605,925

NON RIFLING DRILL BIT I Filed Se'pt. 2, 1969 2 Sheets-Sheet 2 If A, la 0 law WWW/#0 :lNVliNlUR. firm [dime Ma /12 aw/M.

United States Patent 3,605,925 NON RIFLING DRILL BIT Irvine Berscheid, Flin Flon, Manitoba, Canada, assignor to I. J. Berscheid and Associates Limited, Queenston Bay, Winnipeg, Manitoba, Canada Continuation-impart of abandoned application Ser. No. 706,921, Feb. 20, 1968. This application Sept. 2, 1969, Ser. No. 854,667

Int. Cl. E21c 9/00, 13/00 US. Cl. 175-408 2 Claims ABSTRACT OF THE DISCLOSURE My invention relates to new and useful improvements in drill bits, particularly to drill bits containing tungsten carbide inserts and constitutes a continuation-in-part of my application Ser. No. 706,921, filed Feb. 20, 1968, and now abandoned.

Conventional drill bits are tapered so that the cutting head of the bit is greater in diameter than the connecting portion by which the bit is attached to the associated drill rod. This taper is provided to prevent binding within the drill hole and is variable to best counteract the variable conditions encountered in drilling rock or the like in conjunction with drilling machines which alternately rotate and percussively force the bit into the rock being drilled.

Partly because of this taper and the otherwise conventional shape of multi-winged bit heads, the bit can, and does drill an oversized hole, that is, a hole which is greater in diameter than the actual outer diameter of the cutters or inserts. Even when this hole is only slightly oversize, it is unevenly oversize so that diameters vary as we progress along the length of the hole, and also the hole is no longer actually round.

In the more severe conditions, using a four-winged cross bit, the hole is shaped in cross section similar to FIG. 9. The grooves usually spiral to some extent as the bit progresses along the hole and consequently the expression given to this undesirable condition is rifling.

It should be noted that the inscribed circle A in FIG. 9 is actually smaller in diameter in places than the diameter B of the bit. Therefore under the more severe conditions, free rotation of the bit is prevented, and under less severe conditions rotation of the bit is hindered.

As a consequence, severe stresses are exerted on the bit, the rod or rods attached to the bit, and the rock drill, Excessive wear and premature failures of all components are the result.

Rifling also reduces penetration rates considerably.

The purposes of this invention are to provide bits which will accomplish the following:

(a) Prevent rifling of holes and excessive oversize drill- (b) Drill a straighter hole.

(0) Increase penetration rate.

(d) Increase bit life and rod life.

(e) Reduce machine repair costs.

(f) Reduce power requirements for given conditions.

Patented Sept. 20, 1971 These advantages are achieved as follows: Referring to the bit cutting faces as being the top of the bit, the cutting faces of the bit are formed on inserts which have been brazed into the wings of the bit head and then provide that part of the head which makes up the wings holding the inserts, and/or a predetermined part of the head which extends below the base of the insert slots, with an outer wall or similar means which forms a true radius and which wall is also parallel to the longitudinal axis of the shank (or very nearly so).

The diameter of this part of the head should be very nearly as large as the greatest diameter of the cutting edges, but not greater. The part of the head which is at or nearest to the insert base will be of greater diameter than the diameter across the bottom of the inserts. Sludge grooves, if small, can be cut into the bit head in the conventional manner, but since it is preferable to keep as much of the larger circumference of the head, near the insert base, as intact as possible, sludge grooves cut diagonally through this section permit more continuous contact between bit head and wall of hole. This is so that the bit will not be permitted to wobble or gyrate in the hole.

With the foregoing considerations in view, and such other objects, purposes or advantages as may become apparent from consideration of this disclosure and specification, the present invention consists of the inventive concept exhibited in the method, process, construction, arrangement of parts, or new use of any of the foregoing herein particularly exemplified in one or more specific embodiments of such concept, reference being had to the accompanying figures in which:

FIG. 1 is a top plan view of a conventional bit face with additional metal shown in phantom.

FIG. 2 is a partial section through FIG. 1 showing a conventional bit.

FIG. 3 is a view similar to FIG. 2 but showing an embodiment of the invention.

FIG. 4 is similar to FIG. 2 but showing two alternative embodiments of the improved bit.

FIG. 5 is a side elevation showing the preferred embodiment of my improved bit.

FIG. 6 is a side elevation showing an alternative embodiment of the drill bit.

FIG. 7 is a plan view of FIG. 6.

FIG. 8 is a section of FIG. 6.

FIG. 9 is a schematic view showing the effect of rifiing within a drill hole.

In the drawings like characters of reference indicate corresponding parts in the different figures.

In use, as the bit drills due to alternate rotation and percussion, the insert diameter progressively gets smaller. The larger or expanded portion of the bit head will like wise be worn down by rock projecting from the wall of the hole and by the cuttings in which the bit rotates. With correct proportioning to suit the drilling conditions, the head of the bit is self adjusting for diameter. Extreme conditions causing excessive head wear can be compensated for by either vertically extending the expanded portion of the bit head or by welding a more wear resistant metal to the periphery of the head near or below the insert base to allow for as great a continuous expanded periphery as possible.

The bit head being slightly smaller in diameter than the cutters permits a slightly oversized hole to be drilled, but the wall of the hole is normally rough enough and in spots tight enough to allow the head of the bit, by con tacting these tight areas, to keep the cutters centralized, and at the same time keep the head to proper size. Thus a smaller and straighter hole is drilled than is conven tionally possible and rifiing is completely prevented. Pene- 3 tration rate is increased and undue stresses on bits, rods and machine are relieved.

Reference character 10 illustrates a substantially conventional cylindrical connection portion having a head 11 formed on the upper end thereof with a slightly larger diameter than the connection portion 10 as shown in FIG. 2.

A plurality of wings 12 are formed on the upper side of the head and it is conventional to have four such wings Within which are brazed tungsten carbide inserts 13.

Conventional drill bits are shown in solid line in FIG. 1, reference character 14 illustrating sludge grooves to permit the removal of water and grit particles during the drilling operation.

It will be noted, from FIG. 2, that conventional bits have heads 11 which are reduced in diameter from the tips 15 of the cutting inserts to the base of the heads 16. It is this tapering portion which causes the rifling action hereinabove defined and shown in FIG. 9.

I have found that by increasing the diameter of the head 11 remote from the tips 15, that the bit is steadied within the drill hole and prevented from rifling.

In FIG. 1, dotted line 18 illustrates the original diameter of the base of the head and dotted line 19 illustrates the tip 15 diameter.

FIG. 3 show a construction of the bit head in which the bit head is increased in diameter as indicated at 22, beyond the bases 23 of the inserts. This is shown in side elevation in FIG. 6 and in plan in FIG. 7 and although FIG. 7 is reduced in scale to the view shown in FIG. 1, nevertheless the provision of the additional metal is clear 1y indicated and is in fact indicated in phantom as at 24, in FIG. 1.

This gives a head which provides support during the drilling operation and prevents rifling from occurring.

It is necessary to provide sludge grooves through the surface of the wall of the head and it is desirable that these grooves be diagonal as indicated by reference character 25 thus permitting more continuous contact between the bit head and the wall of the hole. This assists in preventing the bit from wobbling or gyrating.

FIG. shows an alternate formation of sludge grooves 26, in which said sludge grooves are provided in pairs and incline upwardly towards a common apex 27. These grooves define a small triangle of metal 28 which maintains the support contact between the increased diameter head and the wall of the drill hole.

As shown by 20 Of FIG. 4, islands of metal can be left on the bit head either at the elevation of the base of the bit insert and extending below this elevation or as shown by 21 of FIG. 4, somewhat below the base of the insert.

These islands of metal are preferably located on the periphery of the head between the longitudinal axis 17 location of the bit inserts as shown by 28 in FIG. 5.

Various modifications can be made within the scope of the inventive concept which is herein disclosed and/Or claimed.

What is claimed as the present invention is:

1. A drill bit for percussive drilling which includes a substantially cylindrical connection portion, a head formed on one end of said connection portion, cutter inserts secured in one end of said head, and means on said head to prevent said bit from rifling when in use, said means including the provision of an increased effective diameter of at least the other end of said head, to a diameter substantially equal to the cutting diameter of said inserts, and pairs of sludge grooves formed in the peripheral wall of said head, the grooves of each pair inclining upwardly and inwardly towards a common apex thereby defining a substantially triangular island of metal on said head and between said cutter insers, for supporting said bit in the hole during use.

2. In a non-rifling percussive drill bit, the combination of a tubular shank adapted for connection to a drill string, a diametrically enlarged cylindrical head formed integrally at one end of said shank, said head having an inner end at its juncture with the shank and also having an outer end remote from the shank, and a set of cutter inserts mounted in the outer end portion of said head in longitudinally outwardly spaced relation from said inner end of the head, said cutter inserts having a definite cutting diameter, and said cylindrical head having a longitudinally straight cylindrical side surface the diameter of which is equal to the cutting diameter of said inserts whereby to constitute guide means for preventing the bit from rifling when in use, the bit being further characterized in that said straight cylindrical side surface extends longitudinally without interruption from the inner end to the outer end of said head.

References Cited UNITED STATES PATENTS 47,805 5/1865 Dickey -408 1,580,254 4/1926 Karns 175-414X 2,579,712 12/1951 Tilden 175-408X 3,128,836 4/1964 Hj'ailsten et al 175-408 3,136,377 6/1964 Lofquist 175-408 JAMES A. LEPPINK, Primary Examiner U.S. Cl. X.R. 175-410, 414 

